TORONTO -- By now the back story to “Gravity,” Alfonso Cuaron’s escape-from-space action piece that hits theaters next month -- is becoming almost as striking as the film itself.

There was the possible involvement of several stars -- Natalie Portman and Angelina Jolie were each in talks -- before the lead role went to Sandra Bullock. There were the years of development at Universal before it landed at current studio Warner Bros. There was the fact that Cuaron wanted to make it a long time ago but, in James Cameron-esque fashion, had to wait for four years for the technology to be invented, and even had to invent some of it himself.

That back story took on another layer at the event, which went over like gangbusters to the audience of 2,000 and helped paint the film as one of the commercial breakouts of the festival, if not yet an awards one.

To make the movie, Bullock told the crowd she spent long hours by herself being whipped around a sound stage with nothing but hundreds of cameras as company. The Oscar winner called the experience "lonely” and said there was “frustrating, painful isolation" on set, then quickly qualified it “but in the best way.”

The actress, who is on-screen for long stretches by herself, joked that all the solitude gave her some resentment for the filmmakers, but she tried to put it to good use. “All your hate and your anger and your rage, you give it to the work,” she said, perhaps only semi-jokingly.

“Gravity” follows Bullock’s Ryan Stone, a researcher on her first trip to space who, along with a veteran astronaut (George Clooney), is stranded outside her craft and forced to traverse the blackness to get to a space station that will offer transport home.

Cuaron acknowledged/reinforced Bullock’s sentiment, noting that he was aware he was putting his actors under a certain kind of duress. "The challenge was gravity, both the film itself but also ... because the movie takes place in zero gravity,” he said. “And the challenge was, how can actors perform under those conditions."

Written by Cuaron with his son Jonas Cuaron, "Gravity" takes place almost entirely in space, a place rendered so realistic it’s possible for right-thinking people to wonder if some of it was shot there. The excitement comes from seeing humans cut loose in space in a frantic -- but also oddly poetic -- bid to get home.

Stone's isolation and personal arc, particularly in one melancholy scene, has a way of making audiences contemplate the vastness of space. But it also brings on a more intimate emptiness. Indeed, filmmakers say that despite the full-throttle genre aspects of “Gravity," they hoped for a psychological effect as well.

“We wanted to create a 90-minute roller-coaster ride that had you trapped to your seat,” Jonas Cuaron said. “But while you were doing that, we wanted an emotional ride also.”